Method of sizing paper



Patented Apr. 2, 1940 PATENT OFFICE alarm mrrnon or srzmo rarna Arthur Reilly, Westbrook, Maine, author to 8'. D. Warren Company, Boston, Man, a corporation of Massachusetts No Drawing. Application October 15, 1986,

Serial No. 1i|5,831

The manufacture of paper, and particularly of sized paper containing alkaline nller, forms the subject matter of this invention.

It is well known that the sizing of paper stock s containing an alkaline filler (e. g. calcium carcustomarily To obtain sizing in the production of paper containing alkaline filler it is customary to use one or more of the following procedures: (1) the rosin-size is replaced or supplemented by wax- I size; (2) sizing or size-restoring agents are applied to the formed" paper-web itself; (3) the ,minimizing" method is used whereby addition of alum is made to the stock after it leaves the machine-chest and immediately before it runs out on the paper-machine wire, Although such methods are to a greater or lesser degree effective in producing sizing in alkaline filled paper, they are disadvantageous in use owing to adverse eflects upon paper qualities other than sizing and/or to increased complexity and difliculty in machine operation.

The desirability is apparent, therefore, of an effective method of sizing alkaline-filled paper by means of rosin-size, in which no involved procedure is required, and by which no desirable quality of the paper is sacrificed. It is accordingly one object of this invention to'provide a method of sizing paper containing alkaline filler by means of rosin-size, whereby the usual operations carried out in beater-sizing are sufilcient. A further object is to use a protective colloid to prevent, or greatly decz ease, the deteriorating action of the alkalinefiller upon the rosin-size precipitate. Another object is to produce paper containing alkaline filler and sizing material precipitated from a size containing rosin-soap and a protective colloid. Other objects and advantages will be apparent as the description proceeds.

It is old to use a protective colloid to prevent the curdling of rosin-size by hard water so that upon subsequent precipitation 'of the size by alum there is produced a much finer size flock than that'yielded by curdled size and alum. In such u a case, however, the furnish is rendered permathat is, the

nently acidic by the alum, so that once the size has been precipitated by the alum it is thereafter unaflected by the furnish. when alkaline filler is present in the system, however. the condition is changed radically. I

The first action of a protective colloid used in rosin-size added to a furnish containing alkaline filler is possibly analogous to that which it gives in the presence of hard water; that is,,the size is protected from curdling prior to being precipitated by alum or other precipitant. Any analogy between hard water and alkaline filler ends, however, with the preliminary stage of protection against curdling. For containing alkaline filler it is not possible to render the stock permanently acidic without destroying all the alkaline filler. The most that can be done is temporarily to depress the hydroxyl concentration for a matter of minutes. If such alkaline-filled stock si'zed with unprotected rosinsize and alum is made up into paper during or within a few minutes following the period of transient hydroxyl depression (according to the minimizing principle), the paper may have a considerable degree of sizing, 0n the other hand, 26 if the size-precipitate is allowed to remain for more than a few minutes in contact with the alkaline furnish, its sizing efilcacy is greatly lessened by the alkalinity, and for practical purposes,

barring the additional use of restoring agents, 30 Q may be considered to be destroyed I have found that the size-precipitate can be so formed and protected against loss in sizing efiicacy by the use of suitable protective agents in the size that its sizing ability may be retained in large measure while in contact with alkaline filler for a period of at least several hours after precipitation. The protective action of the colloid upon the size-precipitate is distinct from and in addition to its action in preventing initial curdling of the size emulsion. The success I have achieved in sizing a1- kaline-filled paper by use of rosin-size containing such a colloid is largely due, I have found, 'to the resistance of the colloid protected size-precipitate against the destructive effect of excess alkaline filler.

In the practice of the invention there is added to a solution or emulsion of rosin-size (i. e. a rosin-soap with more or less free rosin dispersed therein) a quantity of protective colloid (e. g; casein) equal in weight to 4% or more of the weight of the rosin. The so-protected size is mixed in any customary manner with other ingredients going to make up a fibrous furnish for alkaline-filled paper, and the size is precipitated as in the case of paper stock by a size-precipitant (e. g. an aluminum salt) before the stock is run out on a web-forming device.

naturally will vary depending upon the particular colloid used and upon other conditions in the system. In-'g eneral',.'however, a colloidto rosin ratio of 1 to 10 is usually 'eflective in producing improved sizing. As the ratio decreases below 1 to 10, the protective action drops rapidly until it becomes negligible at ratios below about 1 t0 25. On the other hand, as the colloid-rosin ratio increases above 1 to 10 the protective actioninever, in the case of some of the agents, casein, for example, the increase in quantity of protective agent has an undesirable tendency to increase the stabilityoi foam in the system. Ac-

cordingly, inusing those agents that do stabilize the foam, it is-ordinarily not desirable to increase the colloid-rosin ratio above vl tov 5,. unlessan eillcient foam-killer is also'usedin the system. In 3 case the protective agent is one thathas no appreciable effect upon foam stabiliza tion"-' (forinstance, oxidized starch), it may be'u'sed in'quantity equal to or greater than the quantity of rosin if desired. p

zwhile the protected size and/oralum may be added at any convenient time or at any desired point in "the system, provided only that the alum is not wholly consumed by the alkaline. filler before contacting the size, it is preferred to add both the protected size and at least part of the alum in thebeater, for in such case any objectionable foam contributed to by the use of the protective colloid has a longer time in which to be dissipated. By the term rosin-size as used herein is meant various known sizes in which at least 45% of the rosin present is in a saponified condition. Such sizes include the ordinary rosin-sizes of commerce which consist oi sodium or ammonium resinate, with or without unsaponified rosin dis-' persed therein. Examples of colloidal materials found effective in protecting the sizing material from deterioration by the alkalinity-of the furnish are: blood albumen, casein, corn protein, gelatine, glue, locust-bean gum, oxidized starch and soy-bean protein. Naturally these materials are notequally eilective. Each, however, is capable of giving a degree of protective action when present in the rosin-size in a concentration fall- Example 1 A furnish was prepared containing the following materials:

- I Parts Soda fiber 125 Sulflte fiber 65 Calcium carbonate 160 Aluminum sulfate This was beatenlightly at 5% consistency.

The optimum ratio of protective colloid to rosin Toeach of aliquotpartsof thisfurnishwas added rosin-size containing rodn equal to 3% of the weight of the furnish and alum equal to 6% of the weight of the furnish. I

The sized furnish was made up into sheets,

pressed and dried.v The sheets were of approxi- 'mately 50 lb. basis weight, air-dry. The sheets were made exactly alike except that the rosin- -size used (a sodium resinate emulsion containing about 40% of its rosin in unsaponiiled form) for different sheets contained different protective agents. In each case} the 'protectlve agent amounted to-% 'of?th'e'=-. weightof the rosin creases to some extent. At thesam'e time, howr t v feathering'wh'en written upon'with pen and ink,

are -shown in the-following table:

i-Seconds *7 I I v =.,{,,i. Writing resistance Protective agent P tl q Felt Side bide Feltside Wire side None...... 2 2; Poor Poor. Casein (dissolved by 1 ammonia) 4..-... 8 v7 Fair Fair. Oxidized sage starch (low v viscosity) (dissolved by hot water)... i 7 6 Fainto good Fairtogood. Y Oxidized, corn starch (high viscosity) (dissolved by hot water)... 12 8 do Do. Locust bean gum (dissolved by hotwater)... 11 8 Fair Fair. Corn protein (dissolved by ammonia) i2 9 Fairtogood Fair to good. Blood albumen (dis- 'solvedb cold water).- 8 6 Fair Fair. Gelatin igh-grade) (dissolvedbyhotwater) l3 10 Good Good. Animal glue (low-grade) (dissolvedbyhotwater) 7 7 Fan Fan'togood. Soy bean protein (dissolved by ammonia)... i0 6 Fairtogood Good.

Example II A furnish was mixed in the beater in the following order:

Pounds Soda fiber 1260 Suliite fiber 285 Starch (cooked) 35 Protected size containing:

Rosin (as sodium resinate 60% and free rosin 40%) 18 Casein (dissolved by ammonia) 2 Aluminum sulfate 40 Calcium carbonate 570 Later 12 pounds more of alum was added to the machine chest. v

The paper was run out onaFourdrinier wire and pressed, dried and calendered as usual to give 60 1b. paper (25 x 38-500). s

' Sizing an would. mum

Ink floution. weeeonds. anaconda. Pan andink Humbug--. Excellent Excellent. llwampie m The following furnish was prepared:

' Pounds Sulfite fiber 855 Soda fiber I 880 Broke containing calcium carbonate"--- 290 Aluminum sulfate 10 Starch (cooked) To this mixture. after beating but before dropping from the beater, was added Casein (dissolved by borax) 4 Aluminum sulfate Later '10 lbs. of aluminum sulfate was added in the machine chest.

The furnish was made up in the usual way into 55 lb. paper 25 x 38500).

paper in the usual way. By

The sizing by ink flotation was 103 seconds on the felt side.

Example IV The following furnish was mixed in the order shown:

. Pounds Sulfite fiber 400- Soda fiber 1000 Broke (coated paper) 500- Aluminum sulfate 50 Calcium carbonate 1600 Protected size containing:

Rosin (as ammonium resinate 50% and free rosin 50%) 0 Casein (dissolved by ammonia) 9 dumped.

The furnish was then made up into 50 lb. the flotation test the paper on the felt side showed 46 seconds sizing.

. By the method here disclosed in which rosins'ize containing a protective agent equal, to at least 4% of the weight of the rosin is precipitated in a fibrous furnish going to make paper containingalkaline filler, and in which the sizeprecipitate is protected against the hurtful effect of the alkaline furnish by the said protective agent, paper is produced having sizing qualcated above in that'it ity markedly superior to that obtainable under the same conditions without the use of the protective agent. The customary routine of paper making can be followed without requirement of special equipment or special control methods.

The sizing produced is reliable and satisfactory for many purposes. I

The paper product is characterized as indiis a paper containing an alkaline filler, an aluminum resinate and/or alumina-resin combination size, 1. e. a sizing material derived chiefly from a rosin soap and alum or its equivalent, and

aprotective colloid.- ,It is generally conceded that in making ordinary papers (1. e. papers containing no reactive filler) saponified rosin is more effective than mechanically dispersed rosin inimparting sizing. Although authorities disagree as to the exact mechanism of sizing, it is probably true that saponifled rosin when acted on by an aluminum salt is precipitated as aluminum resinate and/or as an association of minute rosin particles adsorbed upon aluminum hydroxide or alumina, said adsorption being more intimate and eflective than is possible to achieve with rosin merely mechanically dispersed.

In furnishes containing alkaline filler, unless protected, aluminum resinate is not formed, and

if added as such it is destroyed and the effective association of rosin and alumina is deleteriously afiected by the alkalinity to the point that sizing is substantially destroyed. The effect of the colloid in the present invention is that the colloidby its presence makes possible the formation of aluminum resinate and keeps the precipitate stable, and further protects the rosin alumina association from the harmful efiect of 1 alkalinity. Consequently paper made by this method retains, and in effective form, the colloid protected aluminum resinate and/or rosinalumina association, substantially unafiected by the action of the alkaline filler.

I claim:

1. Method of sizing paper containing alkaline filler which comprises forming a furnish comprising fibrous material; alkaline filler, a rosin size precipitant and a rosin size at least 45% of the rosin content of which is saponified, said rosin size containing a protective colloid of the group consisting of blood albumen, casein, corn protein, gelatine, glue, locust bean gum, oxidized starch and soy bean protein in quantity amounting to at least 4% of the weight of rosin in the rosin size.

2. Method as defined in claim 1 in which the protective colloid is casein.

3. Method as defined in claim 1 in which the protective colloid amounts to from 4 to 20% of the rosin content of the rosin in the size.

4. Method-as defined in claim v1 in which the ratio of protective colloid to rosin in the rosin size is at least 1 to 10.

5. Method as defined in claim 1- in which the ratio of the protective colloid to the rosin in the rosin size is from about 1 to 10 to about 1 Y 6. Method as defined in claim 1 in which the ARTHUR may. 

